This invention relates generally to compositions for disinfecting substrates as well as to processes for preparing and using such compositions.
The term "disinfectant" is used in this specification to broadly include any substance or composition that disinfects, sanitizes, deodorizes, sterilizes, or kills germs.
The use of chlorine compounds in various types of disinfectant compositions is well known. Chlorine compounds suggested for use in this regard include, for example, sodium hypochlorite, used in World War I as a wound irrigant, and chlorinated phenols such as m-chlorophenol. These compounds have increased bactericidal activity and reduced toxicity, in some instances, when compared to nonchlorinated phenols. Thus, m-chlorophenol has a phenol coefficient of 5.8 (S. aureus) to 7.4 (B. typhosus). Other chlorine compounds having some form of disinfectant utility include, for example, chlorine gas itself, chlorine dioxide, chloramine T, calcium hypochlorite (a standard swimming pool disinfectant), chloropicrin (a larvicide), chloroform (a fumigant), chlordane (an insecticide), and chloromycetin (an antibiotic).
Chlorine dioxide in particular has been found to be an especially effective disinfectant. This compound is quite versatile and has long been used as a bleaching agent such as in the oxidizing of the natural colorant present in cotton, wood pulp and other cellulosic fibrous material. In such uses, chlorine dioxide, though performing an oxidizing function, is nevertheless non-injurious with respect to the fibrous material.
Additionally, chlorine dioxide has long been used in the treatment of water supplies and a precursor is currently available commercially in powder form for use in swimming pools and in liquid form for household and industrial cleaning and disinfecting. In general, chlorine dioxide is superior to gaseous chlorine in the removal of odors and tastes, and in destroying and removing algae or other organic material. Moreover, chlorine dioxide is considered at least as effective as, if not superior to, chlorine gas as a bactericide, virucide or sporicide. Chlorine dioxide is further advantageous in that its antiseptic properties are not as sensitive to pH as chlorine-i.e., chlorine dioxide retains its disinfectant capacity to a significantly greater extent and over a wider pH range than does gaseous chlorine.
Despite the manifold advantages associated with the use of chlorine dioxide for the aforedescribed and related purposes, certain difficulties are nevertheless encountered in practice. Thus, chlorine dioxide as a concentrated gas is explosive and poisonous and accordingly is usually not shipped in the gaseous state to the medium or small user. It has thus become common practice to employ a chlorine dioxide-liberating compound such as sodium chlorite powder which is much safer from the standpoints of storage, shipping and handling. Generation of the chlorine dioxide from sodium chlorite or other chlorine dioxide liberating compound is usually effected by addition of acid, bleach (hypochlorite), or chlorine to the chlorine dioxide liberating compound.
The acid generation of chlorine dioxide is generally effected with the use of a relatively inexpensive inorganic acid, e.g., hydrochloric acid, sulfuric acid and the like. Other acids such as phosphoric or acetic acid (vinegar) have also been used.
Canadian Pat. No. 959,238 to Callerame discloses such a conventional method of producing chlorine dioxide by reacting an alkali metal or alkaline earth metal chlorite, such as sodium chlorite, with an acid. In general, any acid may be used including strong acids such as sulfuric acid and hydrochloric acid and relatively weak acids such as citric and tartaric. This conventional method of producing chlorine dioxide (ClO.sub.2) uses relatively high concentrations of chlorite and acid. The composition formed by this method is advantageous only for the immediate disinfection of a substrate--i.e., it does not result in a stable chlorine dioxide generating solution but instead provides a rapid generation of chlorine dioxide.
Acid-induced generation of chlorine dioxide from sodium chlorite as heretofore recommended and practiced has proven ineffective in that chlorine dioxide is not generated over an extended period of time. On the contrary, these compositions result in a relatively short concentrated period of chlorine dioxide generation and, once this gas dissipates, the residual system is not useful for disinfection purposes. One approach to compensate for this deficiency, and retain significant residual chlorine dioxide in solution for more prolonged activity is to use a system having an increased concentration of sodium chlorite and acid. This approach, however, may lead to toxicity problems, particularly when the composition is used in an enclosed air space. In addition, such a system would be inefficient, since the amount of chlorine dioxide produced greatly exceeds the amount needed for disinfection.
Another problem stems from the fact that the composition obtained from the interaction of the relatively high concentrations of sodium chlorite and acid materials used in the past can be injurious to health. Significantly, the toxicity problem imposes severe limitations on the general utility of the disinfectant composition, particularly with respect to the treatment of human beings.
These prior methods result in the nearly complete and rapid conversion of the majority of the chlorite precursor to chlorine dioxide which is then used as a gas, or in solution.
The above-noted problems with using chlorine dioxide as a disinfectant were solved to some extent by the use of a composition comprising a water soluble chlorite, such as sodium chlorite, and lactic acid. As disclosed in U.S. Pat. No. 4,084,747 to Alliger, this particular composition possesses improved disinfectant properties, properties not attained by using the same composition but replacing the lactic acid with other acids such as phosphoric acid, acetic acid, sorbic acid, fumaric acid, sulfamic acid, succinic acid, boric acid, tannic acid, and citric acid. It would be preferable from the standpoint of economics and acid availability to be able to use acids other than lactic acid, still obtain disinfectant utility, and maintain control over the rate of formation of chlorous acid and thereby chlorine dioxide.
The search has continued for improved compositions for disinfecting various germ carrying substances and improved disinfectant methods. This invention was made as a result of that search.